The P2X7 purinergic receptor (previously known as P2Z receptor), which is a ligand-gated ion channel, is present on a variety of cell types, largely those known to be involved in inflammatory/immune process, specifically, macrophages, mast cells and lymphocytes (T and B). Activation of the P2X7 receptor by extracellular nucleotides, in particular adenosine triphosphate, leads to the release of interleukin-1β (IL-1β) and giant cell formation (macrophages/microglial cells), degranulation (mast cells) and proliferation (T cells), apoptosis, and L-selectin shedding (lymphocytes). P2X7 receptors are also located on antigen-presenting cells (APC), keratinocytes, salivary acinar cells (parotid cells), hepatocytes and mesangial cells.
P2X7 antagonists are known in the art, such as those described in International Patent Publications WO 01/46200, WO 01/42194, WO 01/44213, WO99/29660, WO 00/61569, WO 99/29661, WO 99/29686, WO 00/71529, and WO 01/44170, as well as in WO2003042191.
Benzamides, heteroarylamides and reverse amides for uses other than inhibition of the P2X7 receptor are described in various publications, such as International Patent Publications WO 97/22600, EP 138,527, WO 00/71509, WO 98/28269, WO 99/17777 and WO 01/58883.
Antagonists of the P2X7 receptor are being identified for the treatment of human disease (see e.g., Alcaraz et al. (2003) Bioorg Med Chem Lett. 13(22):4043-4046; Baxter et al. (2003) Bioorg Med Chem Lett. 13(22):4047-4050). There is a need for additional compounds, compositions, and methods of preparing compounds that can inhibit the P2X7 receptor for use as pharmaceutical agents.